This adds the following histograms recorded corresponding to
V8.GCFinalizeMC phases:
- V8.GCFinalizeMC.Clear
- V8.GCFinalizeMC.Epilogue
- V8.GCFinalizeMC.Evacuate
- V8.GCFinalizeMC.Finish
- V8.GCFinalizeMC.Mark
- V8.GCFinalizeMC.Prologue
- V8.GCFinalizeMC.Sweep

Bug: chromium:850508
Change-Id: I47adc125a9a28436d09e35db68a8e8198cbee2dd
Reviewed-on: https://chromium-review.googlesource.com/1091311
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53614}